• 대한치과보철학회지
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• 제34권4호
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• pp.833-849
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• 1996

The material of choice for functional and esthetic reconstruction of maxillofacial defects is silicone. Silicone has appropriate physical properties for maxillofacial prosthesis but it has weak edge strength. Therefore, a proper combination of silicone and polyurethane sheet is recommended to improve this weakness. Various primers are also used to enhance the adhesive strength between silicone and polyurethane sheet. The purpose of this study was to determine the adhesive strength of silicone and polyurethane sheet. Silicone elastomer mixture was made by admixing MDX4-4210 elastomer (40%) and Silastic Medical Adhesive Type A(60%). This silicone elastomer mixture was attached to polyurethane sheet, using one of three different primers(1205, S-2260, or A-304), treated for 1, 2, 4, 6, and 8 hours. These were then polymerized in room temperature, dry-heat oven or microwave oven. Six specimens per each group, a total of 270 specimens were prepared for final test. The differences of T-peel bonding strengths were then determined by a test. The differences of T-peel bonding strengths were then determined by a test method that was recommended by American Society for Testing and Materials C794-80. The results were statistically analyzed using the ANOVA and Mutiple Range Tests(Tukey' HSD). The reults were as follow. 1. Type of primer, primer reaction time, and methods of polymerization showed significant correlation on the T-peel bonding strengths in adhesiveness between silicone and polyurethane sheet. 2. A-304 primer showed statistically higher in T-peel bonding strength than otehr type of primers except for the polymerization in microwave oven with reaction times of 2, 6 hours(p<0.05). 3. No significant differences in T-peel bonding strength were observed among the polymerization methods. 4. The effect of reaction time by the primer type and polymerization method showed statistically significant differences in bonding strength among different reaction times. And in most cases, reaction time of 1 or 2 hours showed higher T-peel bonding strength.

• 폴리머
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• 제36권1호
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• pp.65-70
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• 2012

글리시딜메타크릴레이트(GMA)의 플라즈마 유도 그래프트 공중합을 통해 기재로 사용한 평판형 폴리프로필렌 위에 에폭시 그룹을 도입하였다. 그래프트 공중합은 에멀젼 공중합법을 적용하였고, 기존의 용액 공중합과 비교하여 그 효과를 확인하고자 하였다. 대기압 플라즈마 처리 조건은 RF power 200 W, 처리시간 30초, Ar 기체 유속 6 LPM으로 고정하였고, 처리 후의 대기 중 노출시간 역시 5분으로 고정하였다. 중합반응에서는 GMA의 농도, 반응온도, 반응시간에 따라 표면 그래프트도의 변화를 최적화하였다. 그 결과, GMA 농도 12%, 반응온도 $90^{\circ}C$, 반응시간 5시간으로 중합하였을 때 가장 높은 그래프트도를 나타내었다. 분석 결과, 같은 반응조건 하에서 에멀젼 중합이 용액 중합에 비하여 더 많은 에폭시 그롭 도입에 효과적임을 확인하였다.

• Macromolecular Research
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• 제17권1호
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• pp.14-18
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• 2009

The acceleration effect of various organic acids, such as methanesulfonic acid (MSA), ethanesulfonic acid (ESA), 4,4'-sulfonyldibenzoic acid (SDA), diphenylacetic acid (DPAA), and $\rho$-toluenesulfonic acid (TSA), on the rate of styrene bulk polymerization with 2,2,6,6-tetramethylpiperidinyloxy (TEMPO) and benzoyl peroxide (BPO) was investigated. The addition of organic acids significantly accelerated the rate. Among these organic acids, DPAA showed an efficient rate-accelerating effect with living nature of polymerization. When DPAA was used as a rate-accelerating additive for TEMPO-mediated living free radical polymerization (LFRP), the rate of polymerization was dramatically enhanced, the linearity of reaction kinetics was successfully maintained, and the polydispersity was effectively controlled.

• Composites Research
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• 제32권6호
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• pp.375-381
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• 2019

Multiwalled carbon nanotubes (MWCNTs) are covalently functionalized with isocyanates by directly reacting commercial hydroxyl functionalized MWCNTs with excess 4,4'-methylenebis (phenyl isocyanate) (MDI) and hexamethylene diiosocyanate (HDI). HDI-modified MWCNTs results in a higher surface isocyanate density than MDI-modified MWCNTs. Anionic ring-opening polymerization of ε-caprolactam is conducted using a sodium caprolactam initiator in combination with a di-functional hexamethylene-1,6-dicarbamoylcaprolactam activator in the presence of isocyanate functionalized MWCNTs. This polymerization proceeds in a highly efficient manner at relatively low reaction temperature (150℃) and short reaction times (10 min). During the polymerization, the isocyanate functionalized MWCNTs act not only as reinforcing fillers but also as second activators. Nanocomposites with HDI modified MWCNTs exhibit higher reinforcement and faster isothermal crystallization than MDI modified MWCNTs. The results show that PA6 chains grow more effectively from HDI modified MWCNT surface than from MDI modified MWCNT surface, resulting in stronger interaction between PA6 and MWCNTs.

• Bulletin of the Korean Chemical Society
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• 제31권5호
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• pp.1345-1348
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• 2010

Highly monodisperse polystyrene (PS) nanospheres were fabricated by surfactant-free emulsion polymerization in water using styrene, 2,2'-azobis(2-methyl propionamidine) dihydrochloride (AIBA), and poly(vinyl pyrrolidone) (PVP). The size and distribution of the PS nanospheres were systematically investigated in terms of initiator concentration, stabilizer concentration, reaction temperature, reaction time, and reactant concentration. With increasing AIBA initiator concentration, PS particle sizes are raised proportionally, and can be controlled from 120 to 380 nm. Particle sizes were reduced with increasing PVP concentration. This decrease occurs because a high PVP concentration leads to a large number of primary nuclei in the early stage of polymerization. When the reaction temperature increased, the sizes of the PS particles decrease slightly. The particles grew quickly during the initial reaction stage (1-3 h) and the growth rate became steady-state after 6 h. The PS sizes approximately doubled when the reactant (styrene, PVP, azo-initiator) concentrations were increased by a factor of eight.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.595-600
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• 1993

The heat of reaction has been estimated from heat balance relationships around the reactor. The heat balance equations were formulated with the assumptions that the reactor temperature is uniformly distributed and the jacket temperatures are axially distributed. We have obtained the temperature distribution of jacket contents by FDM. And then, we have rearranged the heat balance equations so that the heat of reaction can be estimated from the finite number of temperature measurements, i.e., temperatures of the reactor contents, at the jacket inlet and outlet, respectively. The proposed method for reaction heat estimation on were applied to industrial batch reactors ; one is ABS polymerization reactor and the other is SAN polymerization reactor. We have also examined the variation of overall heat transfer coefficients for the reactors during reaction.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 1993년도 Fifth International Fuzzy Systems Association World Congress 93
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• pp.1106-1108
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• 1993

This paper deals with an industrial application of a fuzzy feedback combined learning control to an industrial batch free radical polymerization reactor. As a result, the plant has reduced the batch reaction time by 50 minute and stabilized both by 40 percent reduction of the standard deviations of product qualities, such as the total solid content and the graft gum, and by 45 percent reduction of the standard deviation of the batch reaction end time.

• Bulletin of the Korean Chemical Society
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• 제20권12호
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• pp.1433-1436
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• 1999

The 2-(2,4-dimethoxyphenyl)-4-MDO (2) underwent polymerization with ring opening as well as cyclization reaction in the presence of various cationic catalysts such as boron trifluoride, trifluoromethanesulfonic acid, p-toluenesulfonic acid, hydrochloric acid and trifluoroacetic acid. They afforded a mixture of the ring-opened poly(keto ether) and 3(2H)-dihydrofuranone derivative. Both the methylene group and oxygen atom of 1,3-dioxolane ring were participated in the reaction with cationic catalyst. The contents of the polymer and cyclization product were variable according to the acid strength of the cationic catalysts.

• Macromolecular Research
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• 제12권2호
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• pp.213-218
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• 2004

We have performed dispersion polymerization of acrylamide in tert-butyl alcohol/water mixture-using hydroxypropyl cellulose and ammonium persulfate as the stabilizer and the initiator, respectively - to study the effects that the concentration of monomer, initiator, and stabilizer, the tert-butyl alcohol/water ratios as polymerization media, and the reaction temperature have on, among other things, the polymerization kinetics, particle sizes, and molecular weights. The polymerization rate increased upon increasing the concentration of the monomer, initiator, and stabilizer, the water content in the tert-butyl alcohol/water media, and the polymerization temperature. The average particle size of the lattices increased upon increasing the concentration of initiator, the polymerization temperature, and the water content in the tert-butyl alcohol/water media, but it decreased upon increasing the concentration of monomer and stabilizer. The viscosity-average molecular weight increased upon increasing the concentration of monomer and stabilizer and the water content in the tert-butyl alcohol/water media, but it decreased upon increasing both the concentration of initiator and the polymerization temperature.

• Macromolecular Research
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• 제10권3호
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• pp.140-144
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• 2002

Dispersion polymerization of acrylamide was carried out in the media of methyl alcohol/$H_2O$ mixtures using hydroxypropyl cellulose and ammonium persulfate as steric stabilizer and initiator, respectively. The effects of concentrations of initiator and steric stabilizer, amount of monomer, polymerization temperature, methyl alcohol/$H_2O$ ratio, and purification of monomer and nitrogen purge on the particle size of the latices and molecular weight of the polymers were investigated. The average particle diameter increased with increasing concentration of initiator, water content in methyl alcohol/$H_2O$ media, and polymerization temperature, but decreased with monomer and stabilizer concentrations. The viscosity average molecular weight increased with increasing concentrations of monomer, steric stabilizer, and water content in dispersion media, but decreased with initiator concentration and polymerization temperature. The PAM polymers prepared with the purified monomer and the nitrogen purging before the reaction showed the highest molecular weight.